MacBook Pro A1425 it doesn't turn on

[Ledgurra]

hello! hope you are all well. i have a macbook pro a1425 and it won't turn on. i took it to the service center and they said it's fine, it turned on 2 times and then it wouldn't turn on. on the power supply there is a yellow dot that is charging and turns green when charging but when i turn it on it doesn't turn on. i opened it and saw on the motherboard that 2 elements are missing, i am attaching the photos for you to understand better.
thank you all

[mon2]

Share the voltage to ground of ppbus_g3h.

Is this voltage stable?

[Ledgurra]

Share the voltage to ground of ppbus_g3h.

Is this voltage stable?

I disassembled the motherboard to check and measure it, but I saw that a resistor was burned out and a capacitor had been removed. Is it possible for the laptop to work without these elements?

[mon2]

No.

1) Do not take it to this service center again. They are idiots.

2) R6920 is a mandatory resistor that feeds the D6905 dual diode with the power adapter rail. With this resistor missing, the critical PP3V42_G3H_REG cannot be created.




3) C6992 = 4.7uF 0603 @ 25v or higher capacitor. This part should be replaced as well. Start with no power to the board, meter in resistance mode. Measure the resistance to ground of pin # 3 of the dual diode @ D6905. We are testing the resistance at the output of this dual diode which is the same leg as the missing capacitor. We are assuming that perhaps this capacitor was shorted and was removed for this reason by the service center. If the capacitor was indeed with a low resistance, then the current draw will be higher than normal through the dual diode and perhaps burnt out the R6920 resistor. This also implies that the dual diode is defective which is a common fault.

4) To test the dual diode, meter in DIODE mode. Again, no power to the board. Red meter probe onto pin # 1 of this dual diode; black meter probe onto pin # 3 - there should be a voltage. Note the measurement. Now reverse the meter leads and the diode should block - if the diode is not defective you will see 'OL' = over limit on the meter. Repeat with pins # 2 & # 3. Post each measurement.

The dual diode and caps, resistors are very inexpensive.

[Ledgurra]

No.

1) Do not take it to this service center again. They are idiots.

2) R6920 is a mandatory resistor that feeds the D6905 dual diode with the power adapter rail. With this resistor missing, the critical PP3V42_G3H_REG cannot be created.




3) C6992 = 4.7uF 0603 @ 25v or higher capacitor. This part should be replaced as well. Start with no power to the board, meter in resistance mode. Measure the resistance to ground of pin # 3 of the dual diode @ D6905. We are testing the resistance at the output of this dual diode which is the same leg as the missing capacitor. We are assuming that perhaps this capacitor was shorted and was removed for this reason by the service center. If the capacitor was indeed with a low resistance, then the current draw will be higher than normal through the dual diode and perhaps burnt out the R6920 resistor. This also implies that the dual diode is defective which is a common fault.

4) To test the dual diode, meter in DIODE mode. Again, no power to the board. Red meter probe onto pin # 1 of this dual diode; black meter probe onto pin # 3 - there should be a voltage. Note the measurement. Now reverse the meter leads and the diode should block - if the diode is not defective you will see 'OL' = over limit on the meter. Repeat with pins # 2 & # 3. Post each measurement.

The dual diode and caps, resistors are very inexpensive.

I have sent it to that service 3 times for this problem and I am not sending it anymore so I am trying to do it myself by finding the elements and replacing them. Where can I find this element R6920 because with the data it has I can't find it, is there something similar that I can replace it with?

[mon2]

The resistor value is not critical but ideally should be close to the original value of 47R ohms. The physical size is 0805 smd size. First measure the resistance to ground of the output of the dual diode and also confirm the dual diode is not defective. If required, you may need to purchase the resistor + dual diode + missing capacitor from Aliexpress or a nearby vendor. Digikey is common to most customers but if not in a rush, Aliexpress is inexpensive but will take possibly a few weeks for the parts to arrive.

Start with confirming that there is no short on this key power rail. You can replace this resistor with another value of 50R or even slightly lower, say 33R ohms.

From where do you like to purchase your electronic parts?

[Ledgurra]

The resistor value is not critical but ideally should be close to the original value of 47R ohms. The physical size is 0805 smd size. First measure the resistance to ground of the output of the dual diode and also confirm the dual diode is not defective. If required, you may need to purchase the resistor + dual diode + missing capacitor from Aliexpress or a nearby vendor. Digikey is common to most customers but if not in a rush, Aliexpress is inexpensive but will take possibly a few weeks for the parts to arrive.

Start with confirming that there is no short on this key power rail. You can replace this resistor with another value of 50R or even slightly lower, say 33R ohms.

From where do you like to purchase your electronic parts?

I measured the diode and when I put the red wire on pin 1 and the black wire on pin 2 the value comes out 153 and when I invert it I don't get any value and the same with pins 2 and 3. I ordered them on Aliexpress because I'm in Albania and they bring very little mail here and the shipping is very expensive.

[mon2]

If you have any resistor value of 50R ohms or lower, you can replace the missing R6920 to complete the circuit. In general, not recommended but you could even bypass this resistor with a short circuit. Ideally want to have a resistor in place to limit the in-rush currents. When all is well, the power adapter voltage of 16-19v should appear at the output of the dual diode and this in turn should power the regulator (U6990) and offer a stable 3v42 power rail to kick-start the motherboard.

Confirm that the 3v42 rail @ L6995 to ground is not shorted. Remove all power. Measure the resistance to ground of L6995 (either side is ok since this is a coil). What is the resistance value in ohms? If the resistance is too low, then this can also cause the motherboard to not boot due to a shorted component.

Repeat this test by measuring the reistance to ground of pin # 3 of the dual diode @ D6905. Post each measurement.